Ink jet recording is a method of recording a character or image (hereinafter sometimes simply referred to as an “image”) on the surface of a recording medium by ejecting an ink composition as small liquid droplets from fine nozzles. As the ink jet recording system, there are practically used a method of converting an electrical signal into a mechanical signal using an electrostrictive element and intermittently ejecting an ink composition stored in the nozzle head part to record a character or an image on the surface of a recording medium, a method of rapidly heating an ink composition stored in the nozzle head part at a portion very close to the ejection part to generate bubbles and intermittently ejecting the ink composition using the volume expansion due to bubbles to record a character or an image on the surface of a recording medium, and the like methods.
As the ink composition for ink jet recording, in view of safety and printing property, there is generally used an ink composition wherein a dye of various types is dissolved in water, an organic solvent or a mixed solution thereof, and more strict conditions are required for various properties as compared with the ink composition for writing tools such as fountain pen and ballpoint pen.
In recent years, an ink jet printer is employed for the preparation of printed matters for advertisement. Since the printed matter prepared is disposed not only indoors of course but also outdoors sometimes, a high image-preserving property is required. The printed matter is exposed to various lights including sunlight and outside airs (e.g., ozone, nitrogen oxide, sulfur oxide), and hence attempts are being made to develop an ink composition excellent in the fastness to light and gas.
With regard to cyan dyes, cyan ink compositions excellent in fastness to light and gas have been developed (see, e.g., a pamphlet of WO02/060994). However, in the case of a metal phthalocyanine-base dye attempting improvement of gas resistance, a reddish view phenomenon (hereinafter referred to as a “bronzing phenomenon”) is sometimes observed at the portion of high-duty printing such as solid printing (full solid of 100% duty). In such a case, since a color balance as the entire image becomes non-uniform and the image quality is decreased, improvements thereof are desired.
Furthermore, in recent years, a gloss paper is employed in many cases as a recording medium having a feeling close to photographic touch, however, due to a bronzing phenomenon caused by a specific color, the gloss feeling on the printed matter surface is fluctuated to seriously impair the feeling of image. Therefore, also from the standpoint of maintaining the uniform gloss feeling of the whole image, improvements are strongly desired.
Moreover, with regard to the ability of light fastness, the ability of a magenta ink composition is lowest and the composition restricts the life of light fastness of an ink set, so that a magenta ink composition excellent in light fastness and gas resistance has been developed (JP-A-2002-371079) but further improvement in moisture resistance has been desired.
As a means for solving these problems, the present inventors have proposed incorporation of an aromatic compound having a carboxyl group into an ink composition (JP-A-2002-254611, JP-A-2003-090345, and JP-A-2003-339668). It is confirmed that the above aromatic compound having a carboxyl group is remarkably excellent in an effect of improving the bronzing phenomenon and results in an outstanding improvement in clogging resistance when the compound is incorporated as a lithium salt or is incorporated together with lithium hydroxide as a neutralizing agent.
In these embodiments, a sufficient clogging resistance is assured under conditions that the printer is used in a correct state and a printing head is returned to its home position and is capped to wait next printing.